The present invention relates to a composition and process for the preparation of particle or fiber boards with improved properties. The particle or fiber boards of the invention, hereinafter sometimes collectively referred to as "fiberboard", are comprised of wood chips, wood particles and/or fibers, a binder, preferably a synthetic resin binder, a waterproofing agent and optionally fillers, additives and/or processing aids. In the process of the invention, the chips are mixed or treated with the binder and the other additive or filler substances, and pressed into boards. A liquid concentrate is added to and mixed with at least one of the materials or starting materials used for the preparation of the particle and/or fiber boards. Preferably the concentrate is added to the organic chemical binder or the glue bath containing the binder. The components are arranged, spread and/or preformed, and subsequently pressed with a specified compacting pressure at a specified temperature range.
Processes for the preparation of particle and fiberboard utilizing binders, for example urea resins, condensation resins and the like (or glue baths prepared from them), wood chips, fillers, additives and/or processing aids and other additions, and their pressing at elevated temperatures, are generally known. See for example German Auslegeschrift No. 18 01 209.
It is further known to add a flame retardant substance to the chips or fibers during the preparation of the fiber boards. Known agents include borates, phosphates, sulfates or boric acid. It has been discovered, however, that these agents often lead to a loss of quality of the wood material boards because the function of the binders is detrimentally affected. This phenomena is discussed in German Auslegeschrift No. 20 59 163, column 3, lines 46-50.
According to German Auslegeschrift No. 20 59 163, it is therefore proposed to add kaolin as the flame retarding mineral substance in the production of particle and fiber board. Finally, it is also known to dissolve boron compounds and similar salts in the glue baths and to process them for the production of particle boards in the so-called glue undermixing process. However, the process does lead to various disadvantages, for example, acid reactions in aqueous solutions. The jelling time of the condensation resins is thereby shortened to the extent that the hopper life of glued chips is excessively reduced, frequently resulting in defective bonding due to the premature hardening of the glue.
It is further known that boron compounds are absolutely incompatible with certain resins, for example, phenol formaldehyde resins, so that the resins flocculate out upon the addition of the boron compounds.